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WATCH: U.S. President Barack Obama said Russian President Vladimir Putin has a "direct responsibility" to compel pro-Moscow separatists to stop hampering the probe at the site of a downed passenger jet in eastern Ukraine. Speaking on July 21 from the South Lawn of the White House, Obama called on Russia to insist that the separatists grant investigators on the ground "immediate, full, and unimpeded access" to the crash site. He said, "The separatists and their Russian sponsors are responsible for the safety of the investigators." (Reuters)

U.S. President Barack Obama has called on Russia to use its influence to stop pro-Russian separatists from obstructing access to the crash site of Malaysian Airlines Flight 17.

"Russia and President Putin in particular has direct responsibility to compel them to cooperate with the investigation. That is the least that they can do," he said, speaking from the White House.

Obama added that the rebels and the Russians are responsible for the safety of the crash investigators.

He accused rebels of removing evidence from the crash site. "All of which begs the question, what exactly are they trying to hide?"

Obama was vague on future consequences for Russia should it continue to back separatists, saying only that the "costs for Russia's behavior will only continue to increase."

Also on July 21, Ukraine reacted to Russia's version of how MH17 was downed over eastern Ukraine on July 17, saying Moscow appears to be trying to "disown this tragedy."

Spokesman for Ukraine's Security Council Andriy Lysenko said evidence suggests the missile that brought down the plane "was fired by terrorists who received arms and specialists from the Russian Federation."

Russian Defense Ministry official General Andrei Kartapolov said earlier that day that Ukrainian government forces had moved air-defense systems into the area from which the missile originated and that a Ukrainian government warplane was in the area around the time the airliner was shot down, hinting Ukraine might be responsible.

Lysenko said, "To disown this tragedy, the [Russians] are drawing a lot of pictures and maps."

Ukrainian authorities earlier on July 21 said they would hand over control of an investigation into the Malaysian airliner crash to international experts and suggested the Netherlands should lead the process.

Dutch investigators arrived in eastern Ukraine on July 21 and checked the refrigerated train cars with the bodies, near the town of Torez, telling separatists guarding the rail cars the train must be allowed to leave as soon as possible.

The bodies were lying in the field at the crash site for several days.

The train reportedly departed from Torez early on the evening of July 21.

Ukrainian Prime Minister Arseniy Yatsenyuk said 282 bodies of the 298 passengers have been recovered from the crash site.

Ukrainian President Petro Poroshenko on July 21 called for a suspension of hostilities in a 40-kilometer radius around the crash site of the downed Malaysian airliner.

Poroshenko said on July 21 he gave an order to government forces to cease fire in the vicinity of the downed plane in eastern Ukraine to facilitate international investigators' arrival and work at the scene.

The attempts to prevent international investigators from reaching the scene of the crash and reports the personal belongings of some of those who perished had been looted by separatists and others in the area have outraged the international community, particularly those countries whose citizens were aboard the plane.

Dutch Prime Minister Mark Rutte said relatives of the 193 citizens aboard the Malaysian flight were frustrated and angry.

"The whole of the Netherlands feels their anger, the whole of the Netherlands feels their deep grief," Rutte said.

Based on reporting by Luke Johnson in Washington, Reuters, AFP, AP, ITAR-TASS, and Interfax